Clinton’s grasp of policy and ability to turn sentences into paragraphs that express coherent thoughts set her apart in a stark way from her opponent.

LAS VEGAS ― Never has a presidential election revolved so much around human anatomy and, to be specific, genitalia, which made it appropriate that it culminated Wednesday with a debate here in Las Vegas.

That’s a shame, because for 45 minutes or so, the debate was the most rational, issue-oriented one of the three held between Hillary Clinton and Donald Trump. It’s a low bar given the previous forums, but the two candidates had substantive exchanges on the Supreme Court, abortion policy, gun control, immigration, Russia, the economy and so on.

There was no talk of jailing the opposition, or digs at marital difficulties. It was a conversation in which the two candidates thoroughly and sternly outlined their differences.

And then it fell apart, when one candidate ― Trump ― refused to say that he would follow a tradition that goes back more than two centuries of accepting the results of the presidential election if he is the loser. “That’s horrifying,” Clinton told him. That one moment, more than any other, stood out as chilling. And it undermines whatever chance Trump had to present a more moderate face in the remaining two-plus weeks.

Clinton, for her part, turned in her most impassioned performance, beginning with an answer on abortion policy that was the most eloquent defense of reproductive freedom ever delivered on a debate stage.

Her command of the stage often struck a sharp contrast with Trump, who looked low-energy for the first half of the debate, as if the realization was dawning on him that his vanishingly small path to the White House was getting even narrower.

For a while, this created the most unusual of features: a discussion that lacked vitriol. But high roads have been infrequently taken during this election. And by the debate’s midpoint, the all-too-familiar rancor had returned: talk of sexual abuse, rigged elections and character-shaming.

As the night went on, Trump seemed unable to bottle up the rage that has so often taken his debate performances off the rails. “Such a nasty woman,” he said of Clinton. At one point, he complained that he should have won an Emmy for his role on The Apprentice. At another moment, Trump boasted that nobody has more respect for women than he does, and Wallace had to hush the laughter from the crowd.

The moment in the debate that best encapsulated Trump’s entire campaign came when Wallace pressed Clinton on legitimate allegations of cozy relationships with Bill Clinton leading to government contracts for particular companies doing relief work in Haiti. Clinton evaded the question by citing the good work the Clinton Foundation has done, and Wallace tried to press her, but Trump interrupted him, grabbing control of the time and using it to slam the foundation for taking money from Saudi Arabia, and otherwise criticizing Clinton.

Trump, through his inability to just sit quietly, had allowed Clinton to escape the uncomfortable questioning. His reward: Wallace followed up with a question about the Trump Foundation’s indefensible activities.

Clinton’s weakest moment was probably when she was quizzed about her private remarks at a Brazilian bank speech in which she said “my dream is a hemispheric common market with open trade and open borders.” Wallace noted she was paid $225,000 for the private speech. Trump leaned forward. “Thank you,” he said to moderator Chris Wallace.

Instead of attempting to defend the remark ― which, politically, would be extraordinarily difficult ― she said the real question of the night was how her speech became public in the first place, saying that 17 separate intelligence agencies had concluded Russia had obtained the information and provided it to Wikileaks.

Clinton also struggled when facing criticism, immediately breaking into a wide smile, as if to laugh off whatever charge is being leveled. But there was only one candidate on the stage who showed the readiness and qualifications to be president, and there was little question about who it was. Clinton’s grasp of policy and ability to turn sentences into paragraphs that express coherent thoughts set her apart in a stark way from her opponent.

In the end, the debate probably was immaterial with respect to its effect on the election. Clinton is going to win, barring something unforeseeable. What Wednesday night was, instead, was a reminder of how utterly soul-crushing these last 16 months have been and how damaged the body politic might remain even after the election is over.

CLARIFICATION: Language has been amended to more accurately describe the age of U.S. electoral traditions.